About
What it is and where it shows up.
L-Methionine is an essential sulfur-containing amino acid that the human body cannot synthesize and must obtain through diet or supplementation. It is added to foods, infant formulas, and dietary supplements to fortify protein quality and serves as a biochemical precursor to cysteine, taurine, and S-adenosylmethionine (SAM).
Safety summary
The regulatory and scientific consensus.
L-Methionine is well-tolerated at normal dietary intake levels and is recognized as GRAS by the US FDA under 21 CFR 582.5475. Excessive supplemental doses can elevate plasma homocysteine concentrations, a recognized cardiovascular risk marker. Individuals with hepatic or renal impairment face additional risk because methionine catabolism generates sulfate and ammonia that may accumulate when these organs are compromised.
Regulatory landscape
What food-safety regulators have decided.
| Jurisdiction | Status | Note |
|---|---|---|
| EFSA (European Food Safety Authority) (European Union) | Approved | L-Methionine is a permitted amino acid in food supplements under Directive 2002/46/EC and assessed as safe as a nutritional additive (amino acids functional group) in animal feed under Regulation (EC) No 1831/2003. No E-number has been assigned for direct human food additive use. EFSA FEEDAP Panel (2022) confirmed safety for consumers and the environment.source |
| FSSAI (Food Safety and Standards Authority of India) (India) | Approved | Methionine and its derivatives (e.g., S-Adenosyl-L-Methionine, Methionine p-toluenesulfonate) approved as ingredients for Foods for Special Medical Purposes (FSMP) under FSS (Approval for Non-Specified Food and Food Ingredients) Regulations, 2017. L-Methionine as an amino acid nutrient is also regulated under the FSS (Health Supplements, Nutraceuticals, FSDU, FSMP, Functional Food and Novel Food) Regulations, 2016.source |
| FDA (Food and Drug Administration) (United States) | Approved | Listed as GRAS as a nutrient under 21 CFR 582.5475; CAS 63-68-3 confirmed in FDA GRAS review documentation. No upper daily limit set for food use; dietary supplement doses governed by 21 CFR 101.36.source |
Who should approach with care
Whose guidance would steer them away.
Kidney Disease — Methionine catabolism produces sulfate, ammonia, and homocysteine; supplemental doses may increase uremic load and are best limited or monitored in patients with impaired renal clearance.
Liver Disease — Hepatic transsulfuration of methionine is impaired in cirrhosis; high supplemental doses may cause accumulation of toxic intermediates and risk precipitating or worsening hepatic encephalopathy.
Heart Disease — Excess methionine intake raises plasma homocysteine, a recognized independent risk factor for cardiovascular events; high-dose supplementation should be approached cautiously in those with existing cardiac risk.
Infants — Methionine dosing in infant formula and FSMP is tightly regulated by authorities including FSSAI and Codex; unsupervised supplementation in infants is inappropriate and should only occur under medical supervision.
Pregnancy — While dietary methionine is essential during pregnancy, high-dose supplementation has not been established as safe for the developing fetus and should only be used under medical guidance.
Research citations
The sources behind this verdict.
- 1FDA. Code of Federal Regulations Title 21, Part 582.5475 – Methionine (GRAS Nutrient). ecfr.gov
- 2FDA. FDA CVM Response to GRAS Animal Food Notice AGRN 24 – L-Methionine 90% (CJ CheilJedang Corporation). fda.gov
- 3FSSAI. List of Products/Ingredients Approved under FSS (Approval for Non-Specified Food and Food Ingredients) Regulations, 2017 (as of 2 November 2022), 2022. fssai.gov.in
- 4EFSA. Safety and efficacy of a feed additive consisting of l-methionine produced by the combined activities of Corynebacterium glutamicum KCCM 80245 and Escherichia coli KCCM 80246 for all animal species (CJ Europe GmbH), 2022. efsa.europa.eu
- 5PubMed. Safety and efficacy of l-methionine produced by fermentation with Corynebacterium glutamicum KCCM 80184 and Escherichia coli KCCM 80096 for all animal species, 2020. pmc.ncbi.nlm.nih.gov
Independently researched5 citations